(167b) Multi-Objective Optimisation of Multi-Product Rice Value Chains: A Whole-Systems Analysis of the Environment-Food-Energy-Water Nexus

The tropical environment plays a vital role in global food production [1]. Rice cultivation alone, grown in many tropical countries, feeds more than half of the world’s population [2]. Many nations are seeking to be rice self-sufficient, so they focus on increasing productivity, which results in increasing demands for farming inputs, particularly on water [3]. Annual global rice production requires 1308 Mm³/y with irrigated rice paddies as the highest consumers [4]. While water resources in the tropics may seem abundant, the supply is actually constrained. The hydropower sector, a growing contributor to renewable energy options for tropical countries, is a major competitor for water. The rising demand of domestic water use is another main supply constraint due to the growth of population and urban centers. Disrupted weather patterns due to climate change, which lead to extended drought periods in the tropics, poses a major challenge to a reliable supply [5]. In response to climate change, decarbonisation through bioenergy has been a key potential solution but biomass production aggravates the constrained water supply. The use of crop residues, which is more water-use efficient than planting dedicated biomass crops, could be an alternative [6]. Utilising rice straw and rice husk can potentially improve the water-use efficiency of rice and bioenergy sectors through multi-product rice value chains. Due to the various complex issues along the many activities of rice value chains, which could impact the environment-food-energy-water nexus of a region, systematic and data-driven planning techniques have to be developed. There is a research gap in the literature as most planning and design optimisation models for bio-energy provision developed have placed less emphasis on water consumption [7]. Moreover, there is a need to capture the variability of water consumption across geographical locations and over time within a supply chain [8]. In this study, the Value Web Model [9, 10], a spatio-temporal mixed-integer liner programming (MILP) model, is developed for rice value chains with integrated production of food, energy, fuels and chemicals. The model uses a multi-criteria objective function to evaluate tradeoffs between the maximisation of profit, minimisation of water consumption and minimisation of GHG emissions. Scenarios are developed for optimal value chains, which are water-use efficient in: (i) food production only, (ii) integrated food-energy production, and (iii) integrated food-energy-fuels-chemicals production. New data and insights from the case studies of the Philippine rice sector will be presented in this conference.

Keywords: tropical environment; water-use efficiency; environment-food-energy-water nexus; multi-product rice value chains; multi-objective spatio-temporal optimisation; mixed-integer linear programming.

Corresponding author: Dr Sheila Samsatli. Email: s.m.c.samsatli@bath.ac.uk

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